Mark BackgroundTracingManagerBrowserTest test flaky

BackgroundTracingManagerBrowserTest.CrashWhenSubprocessWithoutArgumentFilter
is flaky on android.

It failed at builds [30767, 30786, 30834, 30835, 30843, 30851, 30868, 30909,
30910, 30919, 30923] of
https://build.chromium.org/p/chromium.linux/builders/Android%20Tests
amongst other failures.

NOTREECHECKS=true
NOTRY=true
BUG=639706
TBR=simonhatch@chromium.org

Review-Url: https://codereview.chromium.org/2272293003
Cr-Commit-Position: refs/heads/master@{#414433}

content/browser/tracing/background_tracing_manager_browsertest.cc

@@ -321,12 +321,21 @@ IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
   EXPECT_TRUE(upload_config_wrapper.TraceHasMatchingString("user-agent"));
 }
 
+#if defined(OS_ANDROID)
+// Flaky on android: https://crbug.com/639706
+#define MAYBE_CrashWhenSubprocessWithoutArgumentFilter \
+        DISABLED_CrashWhenSubprocessWithoutArgumentFilter
+#else
+#define MAYBE_CrashWhenSubprocessWithoutArgumentFilter \
+        CrashWhenSubprocessWithoutArgumentFilter
+#endif
+
 // This tests subprocesses (like a navigating renderer) which gets told to
 // provide a argument-filtered trace and has no predicate in place to do the
 // filtering (in this case, only the browser process gets it set), will crash
 // rather than return potential PII.
 IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
-                       CrashWhenSubprocessWithoutArgumentFilter) {
+                       MAYBE_CrashWhenSubprocessWithoutArgumentFilter) {
   SetupBackgroundTracingManager();
 
   base::trace_event::TraceLog::GetInstance()->SetArgumentFilterPredicate(